Charge transfer dynamics in Ar⁺ + CO

Abstract

Differential cross sections for the charge transfer reaction between Ar + and CO have been measured using three-dimensional velocity map imaging in a crossed beam setup at the two relative collision energies 0.55 and 0.74 eV. We find dominant forward scattering with CO + product ions predominantly in the vibrational levels ν = 6,7 of the electronic ground state X 2 + . This is indicative of a direct resonant mechanism for the two argon spin-orbit states. At both collision energies also an isotropic distribution with product ions exhibiting high internal excitation is observed. This is more pronounced at the higher collision energy, where the first electronically excited state A 2 + becomes accessible. We conclude that the A-state is partially populated by the product ions at 0.74 eV collision energy and suggest that the isotropic distribution stems from the formation of a charge-transfer complex, in concurrence with previously performed studies.

Imaging the Collision Energy-Dependent Charge-Transfer Dynamics between the Spin–Orbit Ground Ar+(2P3/2) Ion and CO

“…19 The imaging experiment with a statistical Ar + ion beam clearly showed that the CO + product is mainly at the v′ = 6 and v′ = 7 vibrational levels and predominantly scattered into the extreme forward region at collision energies of 0.74 and 0.55 eV. 20 This is confirmed by our experimental measurements with an Ar + ion beam prepared exclusively at its spin−orbit ground level, 2 P 3/2 . Furthermore, this experiment is also performed at a much lower collision energy of 0.40 eV, which is close to that of early experiments at the thermal energy and 0.2 eV.…”

“…However, they cannot tell which spin−orbit level of the Ar + ion contributes to the experimental results. 21 In the experiment of Wester and co-workers, 20 an isotropic component in the center of the scattering image was observed, which became more prominent at 0.74 eV when compared with that at 0.55 eV. Because excited electronic state A 2 Π + becomes energetically available only at 0.74 eV for the spin−orbit excited Ar + ( 2 P 1/2 ) ion, the abnormally increased relative amount of the isotropically scattered CO + products at the higher collision energy of 0.74 eV was partially attributed to the onset of the formation of excited CO + (A 2 Π + ) through a complex-forming mechanism.…”

“…However, the unambiguous assignments of the two features described above to the specific spin−orbit levels of the Ar + reactant ion were not made. 20 In the study presented here, a reactant Ar + ion beam specifically at spin−orbit ground level 2 P 3/2 was used. The first predominant feature in the experiment of Wester and co-workers is clearly observed here, as well, unambiguously confirming that the energy resonant charge-transfer mechanism plays a major role at low collision energies for the chargetransfer reaction between the spin−orbit ground Ar + ( 2 P 3/2 ) ion and CO.…”

Progresses in the Study of Low-Energy Ion-molecule Reaction Dynamics※

“…＜4 eV)中, 电荷转移产 物集中分布在前向的小角度范围内, 且相对于碰撞前的 能量变化不大, 表明主要是长程的能量共振 CT 机制起 作用. Wester 组 [21][22][23] 也研究了相对较低能量(E c.m. ＜3 eV) [15][16][17][18][19][20] [20] .…”

“…现今国外只有少数研究组, 而国内只有我 们研究组开展此方向的实验研究. 奥地利的 Wester 组从 实验和理论方面, 对负离子亲核取代(S N 2)及相关反应 过程进行了系统的研究工作 [11][12][13] , 还对部分正离子分子 反应过程开展了研究 [21][22][23][24][25][26] ; 美国的 Farrar 组 [14,[27][28][29][30][31][32] 则重 点研究了 C ＋ 、N ＋ 、O ＋ 等原子离子和各种含氢小分子的 CT 和 DCE 过程. 我们组目前已开展了 Ar ＋ 和双原子分 子和多原子分子的 CT 和 DCE 研究 [9][10][15][16][17][18][19][20] , 澄清了以 前对碰撞 CT 过程的争议, 发现了奇特的立体碰撞反应 动力学机制 [9][10] .…”